It never even occurred to me to worry about dropping them and cracking the glass.

McIntosh has some serious support, if you broke the glass, audio classics (http://www.audioclassics.com/) could replace it for you for a reasonable fee. They also are a great source of buying and selling used Mc gear, and also sell shipping boxes. I used them a ways back when I needed to send a vintage McIntosh preamp to Japan and amp to the states. The original boxes were >20 years old, so not safe enough to ship in, they sent me the perfect original boxes for ~$60/each, not bad as they had the wood board, perfect cut-outs, mounting hardware etc.... More importantly, the pre and amp made it safely to their new homes!!!!!